We found inverse correlations between age at onset of the RA patients and antibody titers, such as bacterin-specific IgM ( R = −0.55, p = 0.01), VtaA9-specific IgM ( R = −0.41, p = 0.05), and close to significance for VtaA10-specific IgM ( R = −0.40, p = 0.06; Figures 2A–C , respectively; Spearman's rank correlations).
We found that only 10% of the patients had positive anti type 2 collagen autoantibodies; clustering RA patients based on the presence of Hps and Pg DNA ( Figures 1A,B ) and of antibodies specific for type 2 collagen (10% of the cohort, Supplementary Figure 1B ), there were no significant differences in terms of disease severity, age at onset, and seropositivity, although Hps + RA patients showed a trend of relatively low titers of ACPA, RF-IgM, and IgA.